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Central University of Technology, Free State (2014)

Drinking water quality and farming practices on dairy farms in the greater Mangaung Metro, South Africa

Esterhuizen, Leana

Titre : Drinking water quality and farming practices on dairy farms in the greater Mangaung Metro, South Africa

Auteur : Esterhuizen, Leana

Université de soutenance : Central University of Technology, Free State

Grade : Doctor Technologiae : Environmental Health 2014

Résumé
Dairy farms produce large volumes of animal waste comprising of manure, urine and dairy wash water. In South Africa, dairy waste is usually discharged onto pastures and land by irrigation or flooding which has been known to pollute groundwater with faecally derived microorganisms and nitrates. This study was undertaken to assess groundwater quality on dairy farms in the greater Mangaung area of the Free State. Secondly, the minor aim was to investigate factors that may influence groundwater quality on the farms. These included farming management practices, dairy farm infrastructure and dairy farm waste disposal. Groundwater quality data was collected on 75 dairy farms in 2009. A follow-up study was undertaken in 2013, however, because many farms had ceased production, only 34 farms were included in this round. The groundwater quality data of the 75 farms assessed in 2009 revealed that many farms were compliant with the South African National Standard for Drinking Water. However, 49% of the farms exceeded the limit for nitrates, 60% for total coliforms and 29% for Escherichia coli. When the data gathered on the 34 farms in 2013 were compared to the same farms’ data of 2009, it was found that 45% of the farms in 2009 and 57% in 2013 demonstrated hardness levels that could pose a risk to sensitive consumer groups, such as infants, the aged and the immune compromised. The groundwater on many farms tested as hard or very hard, while the water on a few farms tested extremely hard. Since water is used in all dairy cleaning operations, these levels of hard water could add an additional cost to the running of a dairy by reducing the life span of equipment and increasing the amount of soap used. On 18.9% of the farms in 2009 and 5.6% in 2013, the counts of coliforms exceeded 1 000 per 100 m l groundwater, posing a serious health risk for all consumers. Groundwater with counts of 10 – 100 coliforms per 100 m l could result in clinical infections in consumers, but counts of 100 – 1 000 coliforms could cause infections, even with once-off consumption. In this study, three of the 2013 farms (8.8%) demonstrated counts of E. coli greater than 100 per 100 m l, posing a serious health risk to the consumers. Counts in the region of 10 – 100 per 100 m l were observed in groundwater of 17.6% of the 2009 farms and 29.4% on the 2013 farms. Therefore, consumers on these farms are at risk of clinical infections. Furthermore, when such poor quality water is used in a dairy, the quality of raw milk and products may be affected. Moreover, the number of farms that presented a health risk increased from 41.2% in 2009 to 50.0% in 2013. One of the most effective ways to communicate water quality information is through the use of an index which aggregates all water quality data into a single value. Through a review of literature, three prominent water quality indexes were selected, evaluated and modified ; the Canadian Council of Ministers of the Environment (CCME-WQI), the Weighted (W-WQI) and the Weighted Arithmetic (WA-WQI). Environmental health limits were assigned to eight selected water quality parameters and Water Quality Index (WQI) values calculated using 2013 data. WQI values were categorised into five classes ranging from excellent to unacceptable. When these results were compared with a manual rating of the data, the versatile W-WQI provided the most accurate description of data.

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